Room-Temperature Ferromagnetism and Nonlinear Phonon Dynamics in Atomically Thin 2H-CrS2 Nanosheets: Implications for Spintronics Applications

There has been a great deal of interest in studying transition metal dichalcogenides (TMDs) as two-dimensional (2D) van der Waals materials because of their remarkable physical properties that make them extremely attractive for optoelectronic devices. In particular, the Cr-based TMDs stand out as a unique phase with their tunable electronic and magnetic properties in addition to valley polarization, making them technologically important materials. In this study, we report the successful synthesis of the phase-pure 2H-CrS2 via salt-assisted chemical vapor deposition, yielding monolayer nanosheets with a maximum lateral size of ∼27 μm and a thickness of 0.8 nm, which was characterized by several complementary techniques, including X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), Raman, and photoluminescence spectroscopy. Moreover, the temperature-dependent Raman study revealed a nonlinearity in both in-plane and out-of-plane vibration modes. A model consisting of anharmonic contributions from thermal expansion, three-phonon, and four-phonon processes has been used to explain the nonlinearity in the vibrational modes. Interestingly, magnetic measurements of the sample demonstrate room-temperature ferromagnetism, with a notably high exchange interaction parameter of 18.08 meV, suggesting a Curie temperature well above the room temperature. Besides, the observation of a hump like feature in the temperature-dependent magnetization at around 100–120 K could be linked to the possible charge-density wave transition. These findings suggest a potential coupling between the anharmonic phonon modes and the ferromagnetic state, where lattice dynamics may influence magnetic ordering via magneto-elastic interactions. This interplay could enable advanced functionalities in CrS2, such as tunable low-dimensional spin-phonon devices or enhanced stability for 2D magnetic applications, opening further avenues for exploring multifunctional properties in TMDs.